Reduced Exosomal miR-22 Promotes Cisplatin Resistance and Migration in Non-Small Cell Lung Cancer Cells Through MDM4...

Cisplatin resistance remains a major obstacle in the treatment of non-small cell lung cancer (NSCLC). Exosome-mediated transfer of microRNAs contributes to tumor progression and chemotherapy resistance. However, the role of exosomal miR-22 in cisplatin resistance and its relationship with mouse double minute 4 homolog (MDM4)-regulated p53 signaling remain unclear.

Parental A549 cells and cisplatin-resistant A549/CDDP cells were used as a wild-type p53 NSCLC cell model. Exosomes were isolated from conditioned medium and characterized by transmission electron microscopy, nanoparticle tracking analysis, and Western blotting. Exosome uptake was evaluated by PKH26 labeling with a dye-only control. Cell viability, migration, and apoptosis were assessed using Cell Counting Kit-8, Transwell, and Annexin V-FITC/PI assays, respectively. A dual-luciferase reporter assay and miR-22/MDM4 gain- and loss-of-function experiments were performed to investigate the underlying mechanism. The p-p53/p53 ratio and the expression of p21, cleaved caspase-3, and γ-H2AX were determined by Western blotting.

A549/CDDP-derived exosomes contained significantly less miR-22 than A549-derived exosomes. Both exosome preparations were efficiently internalized by recipient cells, whereas the processed PKH26 dye-only control showed negligible fluorescence. A549/CDDP-derived exosomes increased cell viability and migration under cisplatin exposure, whereas A549-derived exosomes enhanced cisplatin sensitivity. MiR-22 directly targeted the 3'-untranslated region of MDM4 and suppressed MDM4 expression. MDM4 silencing inhibited cell viability and migration, whereas MDM4 overexpression partially reversed the suppressive effects of miR-22. Furthermore, miR-22 increased the p-p53/p53 ratio, p21, cleaved caspase-3, and γ-H2AX expression and promoted apoptosis; these effects were attenuated by MDM4 overexpression. MDM4 silencing also restored p53-associated DNA-damage and apoptotic signaling suppressed by A549/CDDP-derived exosomes.

In the wild-type p53 A549/A549-CDDP model, reduced exosomal miR-22 contributes to cisplatin resistance through MDM4-associated suppression of p53-related DNA-damage and apoptotic responses. These findings identify the exosomal miR-22/MDM4 axis as a candidate mechanism of cisplatin resistance that requires further validation in additional NSCLC models, animal studies, and patient-derived samples.